Laser oscillation apparatus

Abstract

Provided is a laser oscillation apparatus capable of stabilizing resonance even when finesse of an optical resonator is increased and generating stronger laser light than that of a traditional apparatus by accumulating laser light in the optical resonator. The laser oscillation apparatus includes a laser light source which generates laser light for excitation, a fiber amplifier which generates laser light with a desired wavelength when the laser light generated at the laser light source for excitation is supplied, an optical resonator, an optical isolator which is interposed between the optical resonator and the fiber amplifier and which guides the laser light from the fiber amplifier to one side of the optical resonator while blocking laser light in the opposite direction, a circulation optical path which accelerates resonance as introducing laser light emitted from the other side of the optical resonator and returning the laser light to the optical resonator via the fiber amplifier and the optical isolator, and a modulator which performs amplitude modulation on the laser light in the circulation optical path.

The invention claimed is: 
     
       1. A laser oscillation apparatus which generates pulse light with an optical resonator and a plurality of fiber amplifiers arranged at a circulation optical path, comprising:
 a laser light source which generates laser light for excitation; 
 a first fiber amplifier which includes a mode-locking type amplitude modulator to operate light with a desired frequency to be grown as being an integral multiple of a frequency corresponding to an optical path length of the circulation optical path and which emits pulse laser light with the desired frequency while the laser light generated by the laser light source is entered; 
 an optical resonator which resonates and accumulates the pulse laser light emitted from the first fiber amplifier; 
 a second fiber amplifier which includes an adjustment cable corresponding to a wavelength of the pulse laser light and which amplifies the pulse laser light emitted from the optical resonator; 
 a first photodiode which extracts a part of the laser light from the first fiber amplifier; 
 a splitter which divides an output signal of the first photodiode into two; 
 a first RF amplifier which amplifies one of the two output signals from the splitter; 
 a band-pass filter which extracts an RF signal of the laser light with the desired frequency among output signals of the first RF amplifier; 
 a phase modulator which performs phase modulation of the RF signal passing through the band-pass filter; 
 a second RF amplifier which drives the amplitude modulator with the phase-modulated RF signal; and 
 a second photodiode which monitors the other of the two output signals from the splitter, 
 wherein the pulse laser light is self-oscillation-amplified and accumulated in the optical resonator as circling on the circulation optical path which is structured with the first fiber amplifier, the optical resonator and the second fiber amplifier, and 
 the adjustment cable on the circulation optical path is a cable which finely adjusts the optical path length of the circulation optical path. 
 
     
     
       2. The laser oscillation apparatus according to  claim 1 ,
 wherein the pulse laser light is amplified to at least 10,000 times of strength of the laser light for excitation owing to the self-oscillation amplification. 
 
     
     
       3. The laser oscillation apparatus according to  claim 1 , wherein the optical resonator is a Fox Smith interferometer type resonator including at least two concave mirrors which are mutually faced at a predetermined interval. 
     
     
       4. The laser oscillation apparatus according to  claim 3 , wherein the optical resonator includes a piezoelectric adjustor which finely adjusts a resonator length formed by the two concave mirrors in accordance with the desired frequency laser light. 
     
     
       5. The laser oscillation apparatus according to  claim 1 , wherein the first fiber amplifier and the second fiber amplifier are structured with optical fibers which includes a core to which Yb is doped.